/* Shared course stylesheet: every lesson and reference page links this. */
@import url("https://fonts.googleapis.com/css2?family=Source+Serif+4:opsz,wght@8..60,400;8..60,600&family=Inter:wght@400;600&family=JetBrains+Mono&display=swap");

:root {
  --bg: #fffff8; --fg: #1d1d1b; --muted: #5f5f5a; --rule: #d9d6c8;
  --accent: #8a3b12; --accent-soft: #f4e7dc; --panel: #f6f4ea;
  --ok: #2e6b3a; --ok-soft: #e1efe2; --bad: #9b2c2c; --bad-soft: #f6e1e1;
  --serif: "Source Serif 4", Georgia, serif;
  --sans: "Inter", system-ui, sans-serif;
  --mono: "JetBrains Mono", Consolas, monospace;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #171716; --fg: #e9e6dc; --muted: #a3a097; --rule: #3a3934;
    --accent: #e3a178; --accent-soft: #3a2a20; --panel: #22211f;
    --ok: #8fcf99; --ok-soft: #1f3324; --bad: #ef9a9a; --bad-soft: #3b2222;
  }
}
:root[data-theme="dark"] {
  --bg: #171716; --fg: #e9e6dc; --muted: #a3a097; --rule: #3a3934;
  --accent: #e3a178; --accent-soft: #3a2a20; --panel: #22211f;
  --ok: #8fcf99; --ok-soft: #1f3324; --bad: #ef9a9a; --bad-soft: #3b2222;
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--fg);
  font: 19px/1.6 var(--serif); padding: 0 16px; }
main { max-width: 42rem; margin: 3rem auto 5rem; }
header.lesson { border-bottom: 1px solid var(--rule); margin-bottom: 2rem; }
.kicker { font: 600 .78rem/1 var(--sans); letter-spacing: .08em; text-transform: uppercase; color: var(--accent); }
h1 { font-weight: 600; font-size: 2.1rem; line-height: 1.2; margin: .4rem 0 .6rem; }
h2 { font-weight: 600; font-size: 1.35rem; margin: 2.6rem 0 .6rem; }
h3 { font: 600 1rem var(--sans); margin: 1.6rem 0 .4rem; }
.lede { font-size: 1.12rem; color: var(--muted); margin: 0 0 1.4rem; }
a { color: var(--accent); text-underline-offset: 2px; }
code { font: .86em var(--mono); background: var(--panel); padding: .05em .3em; border-radius: 3px; }
small, .note { font-size: .82rem; color: var(--muted); }
sup.cite a { font: .7rem var(--sans); text-decoration: none; }

/* Tables that stay readable on phones */
.table-wrap { overflow-x: auto; margin: 1rem 0; }
table { border-collapse: collapse; width: 100%; font: .86rem/1.45 var(--sans); }
th, td { text-align: left; vertical-align: top; padding: .45rem .6rem; border-bottom: 1px solid var(--rule); }
th { font-weight: 600; border-bottom: 2px solid var(--fg); }

/* Callouts */
.callout { background: var(--panel); border-left: 3px solid var(--accent); padding: .8rem 1rem; margin: 1.4rem 0; }
.callout > :first-child { margin-top: 0; } .callout > :last-child { margin-bottom: 0; }
.callout.key { background: var(--accent-soft); }
.source { font: .9rem var(--sans); border: 1px solid var(--rule); padding: .8rem 1rem; margin: 2rem 0; }
.source strong { color: var(--accent); }

/* Ladder diagram */
.ladder { list-style: none; padding: 0; margin: 1.2rem 0; counter-reset: rung; }
.ladder li { counter-increment: rung; display: grid; grid-template-columns: 2.2rem 1fr; gap: .2rem .6rem;
  padding: .55rem 0; border-bottom: 1px dashed var(--rule); font-size: .95rem; }
.ladder li::before { content: counter(rung); grid-row: span 2; font: 600 1.3rem var(--sans); color: var(--accent); }
.ladder b { font-family: var(--sans); font-size: .9rem; }

/* Thread timeline diagram */
.timeline { display: flex; flex-wrap: wrap; gap: .4rem; align-items: center; margin: 1rem 0; font: .78rem var(--sans); }
.timeline .ev { border: 1px solid var(--rule); padding: .3rem .5rem; border-radius: 4px; background: var(--bg); }
.timeline .job { border-color: var(--accent); background: var(--accent-soft); }
.timeline .arrow { color: var(--muted); }

/* Quiz widget (assets/quiz.js) */
.quiz { border: 1px solid var(--rule); border-radius: 6px; padding: .9rem 1rem; margin: 1rem 0; font-family: var(--sans); }
.quiz .q { margin: 0 0 .6rem; font: 600 .95rem/1.45 var(--sans); }
.quiz .opts { display: grid; grid-template-columns: repeat(auto-fit, minmax(12rem, 1fr)); gap: .4rem; }
.quiz button { font: .88rem var(--sans); text-align: left; padding: .5rem .7rem; border: 1px solid var(--rule);
  border-radius: 4px; background: var(--bg); color: var(--fg); cursor: pointer; }
.quiz button:hover:not(:disabled) { border-color: var(--accent); }
.quiz button.right { background: var(--ok-soft); border-color: var(--ok); }
.quiz button.wrong { background: var(--bad-soft); border-color: var(--bad); }
.quiz .fb { margin: .6rem 0 0; font-size: .88rem; min-height: 1em; }
.quiz .fb.ok { color: var(--ok); } .quiz .fb.no { color: var(--bad); }
.score { font: 600 .9rem var(--sans); color: var(--accent); }

details.recall { border: 1px dashed var(--rule); padding: .6rem .9rem; margin: .8rem 0; font-size: .95rem; }
details.recall summary { cursor: pointer; font: 600 .9rem var(--sans); }

nav.pager { display: flex; justify-content: space-between; gap: 1rem; border-top: 1px solid var(--rule);
  margin-top: 3rem; padding-top: 1rem; font: .88rem var(--sans); }

@media print {
  body { background: #fff; color: #000; font-size: 11pt; }
  .quiz button { border-color: #999; }
  a { color: #000; }
  nav.pager { display: none; }
}